Liquid carbon dioxide suitable for discharge at low temperatures and method of filling storage containers for confining the same



D, MAPES 2,521,52 LIQUID CARBON DIOXIDE SUITAB FOR DISCHARGE AT Low TEMPERATURES AND METHOD FI ING STORAGE CONTAINERS FOR C0 NING SAME Filed Jan. 1944 NVENTOR mazgf 5, W4

ATTORNEY Patented Sept. 5, 1950 LIQUID CARBON DIOXIDE- SUITABLE'FOR DISCHARGE AT LOW TEMPEBATURES AND METHOD F FILLING STORAGE CON- TAINERS FOR CONFINING THE SAME Daniel Mapes, West Caldwell, N. J., assignmto VSpecialties Development Corporation, Bloomield, N. J., a corporation oi.' New Jersey Application January 11, 1944, Serial No. 517,822

Claims.

The present invention relates to apparatus for storing fluid pressure media and a method of lling and discharging such apparatus, and, more particularly, relates to containers to liquid carbon dioxide and a method of iilling and discharging the same.

Liquid carbon dioxide is used extensively on land vehicles, vessels and aircraft as a nre-extinguishing medium and as a medium for operating pressure operable devices in the event of an emergency. For example, carbon dioxide may be used in connection with portable fire extinguishers; built in fire extinguishing systems for aircraft, vehicles and vessels; gasoline tank purging or vapor dilution systems for aircraft, speed boats and the like; gun chargers; and emergency bomb bay door or landing gear operating systems.

The liquid carbon dioxide generally is stored in cylindrical metallic containers, known as cylinders, which are provided with suitable discharge valves for releasing the stored carbon dioxide. While these containers can safely withstand relatively high working pressure, safety discharge means usually are provided in the valves or elsewhere for releasing the stored carbon dioxide to the atmosphere in the event the pressure within the containers becomes excessive.

While these containers of liquid carbon dioxide have been used advantageously at normal atmospheric temperatures generally ranging from about 0 to 140 F., considerable diiculties have been encountered where the containers were exposed to sub-normal atmospheric temperatures. Such sub-normal temperatures are encountered at high altitudes or in arctic regions where the temperature may be as low as 65 F. or even lower.

At such low temperatures, the 4pressure in the containers is correspondingly low. For example, at 40 F., the pressure is about 160 pounds per square inch (gauge), at F., the pressure is about 80 pounds per square inch (gauge), and at F., the pressure is about '70 pounds per square inch (gauge). These correspondingly low pressures fail to eiect rapid discharge of the carbon dioxide from the containers.

Also, at low temperatures and low pressures, the snow forming tendency of liquid carbon dioxide is greatly increased, resulting in large quantities of snow which may block the valves, tubing or other passages of a lire extinguisher or re extinguishing system to thereby prevent the carbon dioxide from being discharged.

Also, upon releasing low temperature liquid carbon dioxide from a container, the expansion of a portion of the carbon dioxide will refrigerate the, carbon dioxide resulting in the formation of solid carbon dioxide in the container which cannot be discharged.

In connection with fire extinguishing, the carbon dioxide is discharged from a nozzle, and, upon expansion, is partially converted into a. spray of snow-like particles. Due to the low pressure in the container, the spray may be propelled an insuflicient distance to reach the location of the fire.

Accordingly, an object of the present invention is to overcome the foregoing difficulties and disadvantages by coniining liquid carbon dioxide under pressure in a manner whereby the carbon dioxide may -be effectively discharged at subnormal atmospheric temperature.

Another object is to provide liquid carbon dioxide conned under pressure which is adapted to be safely stored at normal and relatively high atmospheric temperatures.

Another object is to provide liquid carbon dioxide conflned in a container and exerting a sufliciently high' pressure at sub-normal atmospheric temperatures to effect discharge thereof, but exerting a pressure at relatively high atmospheric temperatures which is less than, or does not substantially exceed, the pressure within a normally filled container of liquid carbon dioxide at about the same temperature.

Another` object is to provide a method of lling containers with carbonl dioxide to accomplish the foregoing objects and advantages.

A further object is to provide liquid carbon dioxide conined in a container adapted to be discharged rapidly at low temperature, whereby the carbon dioxide will not be refrigerated to form a mass of solid carbon dioxide which cannot be expelled.

Other and further objects of the invention will be obvious upon an understanding of the illustrative embodiment about to be described, or will be indicated in the appended claims, and-various advantages not referred to herein will occur to one skilled in the art upon employment of the invention in practice.

In accordance with the invention, it has been found that the foregoing objects and advantages may be accomplished by providing a container charged with liquid carbon dioxide and containing an added gas, other than carbon dioxide, under pressure. The container may be of the type generally used for storing carbon dioxide and may be provided with any suitable valve or discharge fitting.' Such a container of liquid carbon' di- 3 oxide may be provided by charging the container with a quantity of gas having a desired Pressure at a given temperature, and charging the container with a desired quantity of carbon dioxide.

A preferred embodiment of the invention has been chosen for purposes of illustration and description and is shown in the accompanying drawing, forming a part of the specication, wherein:

The figure is a fragmentary, longitudinal, sectional view of a container, provided with a valve, illustrating an embodiment of the invention.

Referring to the drawing, there is shown a metallic container I which has a generally cylindrical shape and is adapted for storing liquid carbon dioxide. 'I'he container is constructed in the usual manner, and, for example, may be of the type adapted to safely withstand internal pressures of about 3600 pounds per square inch. One end of the container is provided with an opening I2 in which is secured a suitable valve or discharge tting 14.

'I'he valve I4 has an inlet Il, to which may be attached a syphon tube Il extending into the container, and has an outlet for connecting a hose or the like adapted to conduct the carbon dioxide to a snow forming horn or the like, oi' the type illustrated in United States Patent No. 1,760,274. 'I'he outlet 20 also may be utilized for coupling a pressure gauge thereto as described hereinafter. Intermediate the inlet and outlet, a valve seat 22 is formed for receiving a valve member 24 adapted to control the discharge of the carbon dioxide from the container. By way of example, a manually operated handwheel 26 and a threaded stem 28 are shown, adapted to eilect unseating of the valve member 24.

A safety discharge assembly l0 is provided intermediate the inlet I6 of the valve and the valve seat 22 for discharging the contents of the container to the atmosphere in the event the pressure within the container exceeds a safe working pressure. The safety discharge of the contents of the container preferably is controlled by a disc 32 or the like adapted to be ruptured when the pressure within the container exceeds a predetermined pressure.

In practicing the invention, the container, preferably, is charged with a gas (other than carbon dioxide) or mixture of gases adapted to exist in a gaseous state at the sub-normal atmospheric temperatures contemplated herein. These gases may be air, argon, carbon monoxide, helium, hydrogen, krypton, neon, nitrogen and oxygen. 'I'hese gases all have a much lower critical temperature than the critical temperature of carbon dioxide, which is 87.8 F. The critical temperatures of these gases are approximately as follows:

Thus, at temperatures as low as 60 F., these gases are adapted to exist in compressed gaseous state, and in such state are capable of exerting a pressure oi' at least about 200 pounds per square inch absolute.

For all-around purposes, nitrogen is preferred because of its comparative low cost, its general availability, and its inert properties. 'I'he critical temperature of nitrogen, that is. the temperature at which nitrogen will exist as a gas regardless of the pressure to which it is subjected, is about 231 F. as will be noted from the foregoing. This temperature is well below the temperatures to which the container and its contents may be subjected, thus assuring that the nitrogen will remain in its gaseous state.

Compressed air may be used advantageously because it can be readily produced by means of any suitable compressor usually available at maintenance and supply depots.

Where the carbon dioxide in the container is intended to be used for fire preventing or fire extinguishing purposes, the gases utilized, preferably, should be substantially inert, non-oxidizing, non-combustible, and non-combustion supporting. These gases may be argon, helium, krypton, neon and nitrogen. However, air (which is composed of about 80% nitrogen and about 20% oxygen, by volume) also has been found suitable for this purpose. The oxygen content of the air appears to be sufficiently small to have a negligible eiect. i

A preferred method of iilling the container comprises rst charging the container with a desired quantity of gas and then introducing into the container a desired quantity of liquid carbon dioxide. Alternatively, a, desired quantity of solid carbon dioxide may be placed into the container, and thereafter the container may be charged with a desired quantity of gas, either while the carbon dioxide is in its solid state or after it has been permitted to liquefy by exposing the container to normal atmospheric temperatures or by heating the container. l

'I'he desired quantity of gas may be determined by charging the empty container with gas having a known pressure at a given temperature. For example, the container may be charged with gas having a pressure of about between 200 and 500 pounds per square inch at about 70 F. Alternatively, the desired quantity/.of gas may be determined by noting the increase in weight of the container and its contents when the gas has been introduced.

The desired quantity of carbon dioxide in the container may vary in accordance with the strength of the container and its safe working pressure. However, in compliance with existing Interstate Commerce Commission regulations,

the weight of the carbon dioxide in a container of a given design shall not exceed 68% of the weight of the water at 4 C. which would completely ll the container. `Such 68% illling is known as normal illling capacity. In practicing the invention with such a container, any suitable quantity of carbon dioxide may be placed in the container which does not exceed 68% illling.

The quantity of carbon dioxide -or percent lling, preferably is varied inversely withthe quantity or the pressure of the gas (other than carbon dioxide) in the container.

In order to illustratey the invention, sixteen containers were charged with nitrogen to establish various pressures in the containers at 70 F., and the containers were then partially fllled with various weights of carbon dioxide. One container was charged with carbon dioxide in the usual manner (without rst being chargedwith nitrogen) to serve as comparison standard.

The containers utilized were steel cylinders complying with Interstate Commerce Commission regulations. and rated as l5 pound cylinders. These cylinders have a volumetric capacity adapted to contain about pounds of carbon dioxide when 68% illled, that is, normally lled."

Eachof the cylinders was ilttedy with a dis-A charge valve, as shown, and a pressure lgauge (not shown) coupled to the outlet ofthe valve for determining the pressures within the cylinders at various temperatures.

In Table I, about to follow, Example Nos. 1 to 16 are test cylinders charged with nitrogen at between about 200 and about 500 pounds per square inch and containing from about 8 to 14 pounds oi carbon dioxide (from about' 50% to about 95% normal iilling capacity). More speciiically, the approximate relationship between the weight of the carbon dioxide and the extent the containers are illledisasfollows:

` Per'Cent Weight C01 oi' Normal Filling 8 lbs. 53 liljbs. 67 l1 lbs 73 12 lbs 80 13 lbs. 87 14 lbs. 93

From observation, it was determined that a 15 pound cylinder charged at 70 F. A-with nitrogen contained approximately the following weights of nitrogen at the given charging pressure:

200 pounds per square inch, .41 lb. of nitrogen 300 pounds per square inch, .61 1b. of nitrogen 400 pounds per square inch, .82 lb. ol nitrogen 500 pounds per square inch, 1.03 lbs. of nitrogen librium throughout the cylinder and its contents, f

and pressure readings were taken at the various temperatures.

6 the pressure within the comparison container at 0 I". (Example l?) At 0 F., the pressures within the containers filled inv accordance with the invention were from almost twice as great to about two and one half times as great as the pressure within the comparison container at this temperafture. As will be illustratedin Table II about to follow. these relatively high pressures at sub-'1 normal temperatures provide rapid and eiiective discharge of the carbon dioxide contents of structed cylinders and safety discs, thus, are not required to practice the present invention.

In Table 1I, about to follow, the discharge rates were compared between a cylinder in accordance with Example 8 (12 pounds carbon dioxide, nitrogen at 300p. s. 1.), and a standard cylinder in accordance with Example 17 (15 pounds carbon dioxide), at temperatures of -40, 0 and '10 F., for 75% discharge of the contents of the respective cylinders. The cylinders were tted with a valve l0 havinga suitable discharge horn (not shown) coupled to the outletL 20 by means of a hose. The carbon dioxide was discharged into the atmosphere at about sea level.

Table II Tcmper- Discharge Example No. amm Time Rate F. Seconds LbL/sfc. -65 26. 5 357 -40 24. 0 .392 0 19. 5 .485 20. 5 460 -65 (l) -40 49. 5 .228 0 37. 5 .300 70 27. 5 .410

l Discharge stopped altar about 15% oi the rbon dioxide was discharged duc to Folidiiying ol the carbon dioxide in the valve, and/or cylinder.

From the foregoing table, it will be observed that a normally lled containedl (Example 1'l)` R t- Gauge Pressure in Lbs/sq. in. at Temperature in F. Co N1 al Example No. Lb i G01N: v

s. p. s. lb Wt 8 000 1.3/1 320 400 480 000 120 800 1,040 1,320 1.000 1,000 1,080 8 400 10/1 400 480 500 080 180 040 1,140 1,300 1,040 1,000 2,120 s 500 8/1 480 500 040 100 880 1,040 1,240 1,480 1,140 2,000 2,240 10 800 11/1 800 880 440 520 020 140 000 1,080 1,300 1,500 1,850. 2,150 10 400 12/1 840 400 400 540 040 180 040 1,150 1,400 1,080 1,080 2.200 11 800 18,11 800 080 440 520 020 100 020 1,100 1,840 1,030 1.050 2,200 11 400 14/1 310 400 400 510 010 800 080 1.200 1,480 1,100 2,080 2,880 12 300 20/1 800 380 440 520 020 100 020 1,100 1,400 1,140 2,080 2,440 12 400 15/1 400 440 520 000 100 8:10 1.000 1,220 1,520 1,840 2,180 2,520 12 500 12/1 520 020 120 840 080 1,100 1,400 1,100 2,040 2,400 2,180 10 200 82/1 280 820 800 450 500 080 840 1,000 1,820 1,140 2,100 2,000 18 200 21/1 300 380 440 520 040 100 020 1,120 1,420 1,840 2,200 2,050 13 400 10/1 400 450 520 000 100 aso 1,010 1,240 1,500 1,000 2,500 2,100 14 200 34/1 280 l320 300 450 500 080 840 1,080 1,850 1,100 2,240 2,100 14 800 23/1 :180 400 440 520 040 100 020 1.120 1,480 1,050 2,400 2,050 14 400 11/1 400 520 510 040 180 800 1,040 1,200 1,040 2,120 2,020 3,120 15 80 131 200 200 401 558 134 053 1,445 1,085 2,525

From the foregoing table it will be observed cannot beefiectively discharged at 65 1"., while that at --60 F. the pressures within the containat 40 F. and 0 F., the time requiredv to dis- Y ers filled in accordance with the invention (Excharge of its contents is about twice the Y amples l to 16) were equal or much greater than 75 time required to discharge 75% oi the contentsV r` Avalve at such low temperatures.

present invention (Example 8).

` It will also be observed that the discharge rate of a container in accordance with the invention, at 65 F., is greater than the discharge rate of a normally filledcontainer, at F., and compares favorably with the discharge rate of `a normally filled container at 70 F.

-The high discharge rate is particularly advantageous in cases where the carbon dioxide is introduced into a closed space to extinguish a fire.y In such cases, a high carbon dioxide concentration is rapidly established to effect rapid extin-l guishment of the lire. l

From the foregoing tests, itis also apparent that containers filled in accordance with the present invention can .be effectively discharged at temperatures approaching 70 F., thus indicating that the presence of nitrogen or other gas has a definite eii'ect on preventing the liquid carbon dioxide from solidifying in the container and the This elect is believed to be due to the fact that a portion of the nitrogen or other gas is absorbed by the liquid carbon dioxide to lower its freezing point. It has beenfound that the carbon dioxide in normally iilled containers solidifes at temperatures approaching 70 F., and cannot be discharged.

From the foregoing description and examples,

it will be seen thatthe present invention provides improved containers of liquid carbon dioxide and an improvedl method voi preparing and discharging the same. The invention can be practiced with containers and discharge valves and horns used heretofore and without the use of specially designed equipment. The containers, filled in accordance with the invention, can be speedily discharged at relatively low temperatures. The pressure within the containers at these low temperatures eiects discharge of the contents without tendency to solidify and clog up the valves and the like. sive internal pressures at relatively high atmospheric temperatures. The filled containers can be advantageously utilized for numerous purposes as indicated herein.

While the present invention has been described by way of example in connection with a '15 pound cylinder of the portable type, it will be understood that the invention can be practiced with cylinders of any desired capacity or with banks of a number of such cylinders as heretofore employed in systems for storing and discharging carbon dioxide for 'numerous desired purposes.

As various changes may be made in the form, construction and arrangement of the parts herein, without departing from the spirit and scope of the invention and without sacrificing any of its advantages, it isto be understood that all matter herein is to be interpreted as illustrative and not in any limiting sense.

It is also to be understood that the fonowing claims are intended to cover all the generic and specic features of the invention herein described, and all statements of thescope of the invention which, as a matter of language, might be said to fall therebetween.

I claim:

1. A method of providing for the continuous discharge, from a closure controlled restricted orifice, of carbon dioxide in a, continuous stream even when the temperature at the orifice falls to 60 F.; said method comprising forming, at a temperature within the normal range of atmos- The containers do not have exces- 8.. pheric` temperatures, in a. storage container provided with said orliice a charge capable of exertingv on saidvcontainerat 60 F. a* pressure in excess of about two hundred pounds per square inch and consisting principally of carbonv dioxide and'having as a secondoomponenta gas inert to carbon dioxide and having a critical temperature below 80.5 lF., the weight of the charge lbeing less than that of a normal charge of carbon dioxide. l l

2.,A method of forming a charge in storage containers which comprises the steps of introducing into the containers at normal temperature a predetermined quantity of carbon dioxide and a predetermined quantity of'compressed gas which is capable of exerting a sufllcient pressure-at 60 F. so that the charge of-said gas and carbon dioxide will be confined `under a pressure of at least about 200 pounds per square inch absolute at a temperature of about 60 F., the weight of the charge being less than that of a normal charge of carbon dioxide.

3. A method of forming a charge in storage containers which comprises the steps of first partially lling the containers at normal temperatures with carbon dioxide and then introlucing a gas into the containers which gas is capable Yof exerting a suicient pressure at 60 F. so that the charge of said gas and carbon dioxide will be coniined under a pressure of at least about 200.pounds per square inch absolute at a temperature of about 60 F., the weight of lthe charge being less than that oi" a normal charge of carbon dioxide.

4. A method of forming a charge in storage containers which comprises iirst charging the containers at normal temperature with a compressed gas, and then introducing a predetermined quantity of liquid carbon dioxide, said gas being capable of exerting a sumcient pressure at 60 F. so that thechargeV will be conflned under a pressure of at least about 200 pounds per square inch absolute at a temperature of about 60 F., the weight of the charge being less than that of a normal charge of carbon dioxide.

5. A method of forming a charge in storage containers which comprises the steps of iirst placing into the containers at normal temperature a predetermined quantity of solid carbon dioxide and then charging the containers with a predetermined quantity of compressed gas which is capable of exerting a sumcient pressure at 60 F. so that the charge of said gas and the carbon dioxide upon liquefying will be confined under a pressure of at least about 200 pounds per square inch absolute at a temperature of about 60 F., the weight of the charge being less than that of a normal charge of carbon dioxide.

6. A method of forming a charge in storage containers which comprises first charging the containers at normal temperature with a compressed gas, and then introducing into the containers a predetermined quantity of liquid carbon dioxide to ll the same to between about 50% and about 95% of their normal filling capacity, said gas being capable of exerting a sulcient pressure at 60 F. so that the charge will be conned under a pressure of at least about 200 pounds per square inch absolute at a temperature of about 60 F. y

'1. A method of providing for the continuous discharge, from a closure controlled outlet openeven when the temperature at the opening falls to 60 F., said method comprising introducing into a storage container a charge of gas having a pressure of between about 200 and about 500 pounds per square inch when confined in the container at a temperature of about 70 F., and then introducing liquid carbon dioxide into the container to fill the same to between about 50% and about 95% of its normal filling capacity, said gas being inert to carbon dioxide, having a. freezing point below that of carbon dioxide and being capable of coacting with the carbon dioxide to exert on the container a pressure in excess of about 200 pounds per square inch at 60 F.

8. A charge of fluid medium conned under pressure in a fluid-tight storage container having a closure controlled discharge passage, said charge comprising principally carbon dioxide and a compressed gas inert to carbon dioxide having a critical temperature below 80.5 F.. the weight of the charge in relation to the volumetric capacity of the container being such that the charge is safely conflneable in the container without building up excessive pressures at ternperatures as high as about 140 F. and said other gas being present in proportion to the carbon dioxide to coact with the carbon dioxide to cause the charge to exert on the container a pressure in excess of about two hundred pounds per square inch at about 60 F., whereby said charge is dischargeable from the container at a relatively high rate at temperatures as low as 60 F. without a tendency to solidify and clog the passage through which it is discharged.

9. A charge of iiuid medium confined under pressure in a fluid-tight storage container having a closure controlled discharge passage, said charge comprising principally carbon dioxide and a compressed gas inert to carbon dioxide having a critical temperature below 80.5 F., the weight of the carbon dioxide being equivalent to between about 50% and about 95% of the normal carbon dioxide illling capacity of the container and the ratio of carbon dioxide to said other gas by weight being between about 8 and about 34 to one 45 1,938,036

l0 and the combined weight of carbon dioxide and said other gas not exceeding the weight of a normal charge of carbon dioxide whereby the charge is safely conilneable in the container without building up excessive pressures at temperatures as vhigh as about 140 F., and said other gas being present in proportion to the carbon dioxide to coact with the carbon dioxide to cause the charge to exert on the container a pressure in excess of about vtwo hundred pounds per square inch at about F., whereby said charge is disch'argeable from the container at a relatively high rate at temperatures as low as 60 F. without a tendency to solidify and clog the passage through which it is discharged.

10. A charge of iiuid medium coniined under pressure in a uid-tight storage container'having a closure controlled discharge passage, said charge comprising principally carbon dioxide and a compressed gas inert to carbon dioxide having a critical temperature below 80.5 F., the weight of the charge in relation to the volumetric capacity of the container being such that the charge at F. will exert less pressure on the container than a normal charge of carbon dioxide at 140 F. and said other gas being present in proportion to the carbon dioxide to coact with the carbon dioxide to cause the charge to exert on the container a pressure in excess of about two hundred pounds per square inch at about 60 F., whereby said charge is dischargeable from the container at a relatively high rate at temperatures as low as 60 F. without a tendency to solidify and clog the passage through which it is discharged.

` DANIEL MAPES.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Name Date Hamilton Apr. 3o, 191s Martin et a1 Dec. 5, 1933 Number 

1. A METHOD OF PROVIDING FOR THE CONTINUOUS DISCHARGE, FROM A CLOSURE CONTROLLED RESTRICTED ORIFICE, OF CARBON DIOXIDE IN A CONTINUOUS STREAM EVEN WHEN THE TEMPERATURE AT THE ORIFICE FALLS TO -60*F., SAID METHOD COMPRISING FORMING, AT A TEMPERATURE WITHIN THE NORMAL RANGE OF ATMOSPHERIC TEMPERATURES, IN A STORAGE CONTAINER PROVIDED WITH SAID ORIFICE A CHARGE CAPABLE OF EXERTING ON SAID CONTAINER AT -60*F. A PRESSURE IN EXCESS OF ABOUT TWO HUNDRED POUNDS PER SQUARE INCH AND CONSISTING PRINCIPALLY OF CARBON DIOXIDE AND HAVING AS A SECOND COMPONENT A GAS INERT TO CARBON DIOXIDE AND HAVING A CRITICAL TEMPERATURE BELOW -80.5*F., THE WEIGHT OF THE CHARGE BEING LESS THAN THAT OF A NORMAL CHARGE OF CARBON DIOXIDE. 